Laptop Battery Mod - Adding a Secondary Battery

From 1h 45m of battery life to 6 hours of battery life using some junk from my basement and a used Dell laptop battery.

This mod was done on an Asus Z7100 series laptop (Z71V to be exact). But the theory behind this mod should work on pretty much any laptop, notebook or netbook out there. It worked out better than I ever expected.

Step 1: Open the Laptop Battery.

Open Asus Z71V Battery Pack (Model No. A42-M7)

Opening the battery pack is probably one of the more challenging parts of the project as most battery packs are sealed/glued/welded shut.

I started mine by cutting into the seam at the corners of the battery pack with a utility knife. I managed to get a flat screw driver into the incisions I made with the knife and started to pry the case open. Be very careful to not push the knife or screw driver too far into the pack as you could damage the batteries or battery controller PCB. I pushed my screw driver in too far and knocked a tiny resistor off my PCB. Took me half an hour to get it soldered back on.

Once you have the battery pack open, inspect how the batteries are wired up.

There are Eight 18650 Cells. A red wire for the + end of the series and a black wire for the - end of the series. white, yellow and orange wires for the intermediary charging points.

It is an 8 cell battery that has 2 rows of 4 cells. The batteries inside are Samsung Lithium-Ion 18650 sized cells with an output of 3.7v at 2200 mAh each. They are wired in 2 parallel series' of 4. The specs on my battery state 14.8v with 4400 mAh. Since the batteries are 3.7v each and there are 4 batteries in each series, 4 * 3.7v = 14.8v. There are 2 of these 14.8v series wired parallel to each other. This gives us 2 * 2200 mAh for a total of 4400 mAh at 14.8v.

14.8v and 4400 mAh (milliampere-hours)

After around 3 years of use, this battery had degraded to around 28000 mWh according to Notebook Hardware Control (NHC). It only lasted 100 minutes or less; compared to 3 hours+ of runtime I used to get.